The Insects has been the standard textbook in the field since the first edition published over forty years ago. Building on the strengths of Chapman's original text, this long-awaited 5th edition has been revised and expanded by a team of eminent insect physiologists, bringing it fully up-to-date for the molecular era. The chapters retain the successful structure of the earlier editions, focusing on particular functional systems rather than taxonomic groups and making it easy for students to delve into topics without extensive knowledge of taxonomy. The focus is on form and function, bringing together basic anatomy and physiology and examining how these relate to behaviour. This, combined with nearly 600 clear illustrations, provides a comprehensive understanding of how insects work. Now also featuring a richly illustrated prologue by George McGavin, this is an essential text for students, researchers and applied entomologists alike.

The insects: structure and function.

Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis.

The administration of leptin to leptin-deficient humans, and the analogous Lepob/Lepob mice, effectively reduces hyperphagia and obesity. But common obesity is associated with elevated leptin, which suggests that obese humans are resistant to this adipocyte hormone. In addition to regulating long-term energy balance, leptin also rapidly affects neuronal activity. Proopiomelanocortin (POMC) and neuropeptide-Y types of neurons in the arcuate nucleus of the hypothalamus are both principal sites of leptin receptor expression and the source of potent neuropeptide modulators, melanocortins and neuropeptide Y, which exert opposing effects on feeding and metabolism. These neurons are therefore ideal for characterizing leptin action and the mechanism of leptin resistance; however, their diffuse distribution makes them difficult to study. Here we report electrophysiological recordings on POMC neurons, which we identified by targeted expression of green fluorescent protein in transgenic mice. Leptin increases the frequency of action potentials in the anorexigenic POMC neurons by two mechanisms: depolarization through a nonspecific cation channel; and reduced inhibition by local orexigenic neuropeptide-Y/GABA (gamma-aminobutyric acid) neurons. Furthermore, we show that melanocortin peptides have an autoinhibitory effect on this circuit. On the basis of our results, we propose an integrated model of leptin action and neuronal architecture in the arcuate nucleus of the hypothalamus.

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Leptin activates anorexigenic POMC neurons through a neural network in the arcuate nucleus

Recent advances in integrative studies of locomotion have revealed several general principles. Energy storage and exchange mechanisms discovered in walking and running bipeds apply to multilegged locomotion and even to flying and swimming. Nonpropulsive lateral forces can be sizable, but they may benefit stability, maneuverability, or other criteria that become apparent in natural environments. Locomotor control systems combine rapid mechanical preflexes with multimodal sensory feedback and feedforward commands. Muscles have a surprising variety of functions in locomotion, serving as motors, brakes, springs, and struts. Integrative approaches reveal not only how each component within a locomotor system operates but how they function as a collective whole.

https://science.sciencemag.org/content/sci/288/5463/100.full.pdf

How Animals Move: An Integrative View

We have developed a method for temporal and regional gene expression targeting (TARGET) in Drosophila and show the simultaneous spatial and temporal rescue of a memory defect. The transient expression of the rutabaga-encoded adenylyl cyclase in the mushroom bodies of the adult brain was necessary and sufficient to rescue the rutabaga memory deficit, which rules out a developmental brain defect in the etiology of this deficit and demonstrates an acute role for rutabaga in memory formation in these neurons. The TARGET system offers general utility in simultaneously addressing issues of when and where gene products are required.

https://science.sciencemag.org/content/sci/302/5651/1765.full.pdf

Spatiotemporal rescue of memory dysfunction in Drosophila

1. \n \nThe electrophysiology of the four paired nerves innervating the fly's neck muscles were examined by extra- and intracellular recording and staining with Lucifer Yellow. \n \n \n \n \n2. \n \nUnits that responded to moving black and white gratings and that were, therefore, termed ‘visual’ were recorded in all four neck muscle nerves. These visual motor neurons were direction-selective responding most vigorously to a single direction by excitation. \n \n \n \n \n3. \n \nThe preferred direction and the field of view of visual motor neurons was specific for each of the four neck muscle nerves and generally reflected an organization into horizontal- and vertical-motion-sensitive units. \n \n \n \n \n4. \n \nThe response characteristics of visual motor neurons corresponded to the structural relationship between their dendrites and visual interneurons in the lobula plate or terminals of descending neurons that were themselves associated with specific lobula plate neurons. \n \n \n \n \n5. \n \nVisual units were only a small fraction of all neck motor neurons. A non-visual motor neuron responding to mechanical stimulation of wing and antenna and four mechanosensory fibre tracts associated with the prothoracic neck motor neuropil are described in detail.

The neck motor system of the fly Calliphora erythrocephala. I: Muscles and motor neurons

A serum raised against conjugated octopamine reveals structurally comparable systems of perikarya and arborizations in protocerebral neuropils of two species of Diptera, Drosophila melanogaster and Phaenicia sericata; the latter is used extensively for electrophysiological studies of the optic lobes and their central projections. Clusters of cell bodies in the brain as well as midline perikarya provide octopamine-like immunoreactive processes to the optic lobes, circumscribed regions of the protocerebrum and the central complex, particularly the protocerebral bridge, fan-shaped body, and ellipsoid body. Ventral unpaired median somata provide immunoreactive processes within the subesophageal ganglion and tritocerebrum. Ascending neurites from these cells also supply the antennal lobe glomeruli, regions of the lateral protocerebrum, the mushroom body calyces, and the lobula complex. The mushroom body’s lobes contain immunoreactive processes that originate from processes that arborize in the protocerebrum. The present observations are discussed with respect to similarities and differences between two species of Diptera, one of which has neurons large enough for intracellular penetrations. The results are also discussed with respect to recent studies on octopamine-immunoreactive organization in honey bees and cockroaches and the suggested roles of octopamine in sensory processing, learning, and memory. J. Comp. Neurol. 494: 460 – 475, 2006. © 2005 Wiley-Liss, Inc. Indexing terms: learning and memory; mushroom bodies; locomotion; central complex; octopamine

Comparison of octopamine-like immunoreactivity in the brains of the fruit fly and blow fly.

Publisher Summary Central pattern generator circuits provide rhythmic patterns of activity among connected neurons that mediate walking Local perturbations, such as irregularities in ground height, are relayed to central pattern generators by feedback from many thousands of mechanoreceptors This sensory information is integrated locally by spiking and nonspiking local interneurons that control and maintain patterned firing among motoneurons Local circuits integrate information about leg position, allowing compensatory adjustments at the leg joints for maintaining posture and gait In many insect species, local sensory afferents and the thoracic nervous system could alone maintain forward locomotion Circuits underlying locomotion toward a stimulus source appear to be more complexly organized than those mediating escape behaviors Descending neurons that relay information from the brain to thoracic ganglia have several discrete dendritic domains in the brain, which usually receive sensory inputs indirectly through ensembles of interneurons In addition, many descending neurons that supply leg motor circuits also receive connections from a prominent midline neuropil, called “the central complex” This chapter discusses some of the known properties of this center and speculates about the significance of its structure To date, behavioral genetics, electrophysiology, and comparative anatomy all suggest that the central complex plays a cerebellar-like role in controlling forward locomotion, change of direction, and other limb actions However, before considering the central complex, it is important to outline the segmental organization of the insect brain and to emphasize the unique position of the central complex within the three pre-oral ganglia

A brain region in insects that supervises walking.

The optic lobes of Diptera have been examined by variants of the Golgi-Colonnier selective staining techniques and by reduced silver procedures. All, bar one, of the elements described by the earlier authors (Vigier 1908; Zawarzin 1913; Cajal & Sanchez 1915) have been seen, in part or in their entirely, in these preparations. Many other forms, hitherto unrecognized, have been found. Their perpendicular topographical relationships have been reconstructed in the optic lobe regions. Some lateral relationships have also been reconstructed between elements in regions whose columnar arrangement is clearly discernible in Golgi preparations; these include the lamina and the medulla. In the Diptera the projection pattern of the retina mosaic into the lamina neuropil involves complex chiasmata between the two regions (Braitenberg 1967); these have been confirmed from these species. The retina-lamina mosaic is, essentially, homotopically preserved in the columnar medulla, via long visual fibres and monopolar cells. The medullary mosaic is preserved through its strata by transmedullary cells and the longest small-field amacrine cells. The mosaic is projected to the two regions of the lobula complex by class I cells (see part I). The organization of the tangential cell processes suggests that some of them may interact with large or whole field aggragates of the relayed retinal mosaic. Others, especially in the lobula, may interact with small oval or narrow strip-field aggragates. Although there are many differences of neural form and number of neurons between species, both the Lepidoptera and Diptera have the same fundamental plan of neuroarchitecture.

The Optic Lobes of Diptera

Within the Arthropoda, morphologies of neurons, the organization of neurons within neuropils and the occurrence of neuropils can be highly conserved and provide robust characters for phylogenetic analyses. The present paper reviews some features of insect and crustacean brains that speak against an entomostracan origin of the insects, contrary to received opinion. Neural organization in brain centres, comprising olfactory pathways, optic lobes and a central neuropil that is thought to play a cardinal role in multi-joint movement, support affinities between insects and malacostracan crustaceans.

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Nicholas J. Strausfeld

Papers

The neck motor system of the fly Calliphora erythrocephala. I: Muscles and motor neurons

Comparison of octopamine-like immunoreactivity in the brains of the fruit fly and blow fly.

A brain region in insects that supervises walking.

The Optic Lobes of Diptera

Brain organization and the origin of insects: an assessment